What does the above genetic elements and resistance pattern say about the origin of the strain? To a non-expert like me, the following:

First, that it does not follow the pattern of broad surveys of non-O157:H7 STEC in animals and humans such as in “Phenotypic and genotypic characterization of verotoxin-producing Escherichia coli O103:H2 isolates from cattle and humans.”
Karama M, Johnson RP, Holtslander R, Gyles CL (EU and N. America) and “Antimicrobial resistance testing of verocytotoxin-producing Escherichia coli and first description of TEM-52 extended-spectrum β-lactamase in serogroup O26” .Buvens G, Bogaerts P, Glupczynski Y, Lauwers S, Piérard D (Belgium).

Second, the absence of stx-1 and the presence of stx-2a (VT 2a) as well as the resistance pattern suggests human origin in a carrier infected by (or carrying) a virulent HUS strain. See the above articles and the research on monoclonal antibodies targeting stx-2 as therapeutic treatments for HUS at the Uniformed Services University (O’Brien lab) and Caprion/Ecopia.

Third, this would suggest greater investigation emphasis on contamination at washing-repacking facilities, possibly in Hamburg, including worker health status, conditions of work, or physically inappropriate design allowing contamination (based on testimony and outbreak investigation reports surrounding O157:H7 in spinach). This may be non-standard procedure for a presumed food-borne outbreak.

But I would recommend asking Carlton Gyles at Guelph, or others, who are expert to look at the data pattern.

Dan Cohen
Maccabee Seed Company
Davis, CA

Minkpuppy

For a non-expert, you’ve got some very good points, Mr. Cohen. You definitely have a better idea than I do on how to interpret the data here.

I wonder how many outbreaks have actually been caused by a sick worker or even an asymptomatic carrier? Has it even been considered in outbreaks where they can’t seem to pinpoint a source?

I’m thinking of Typhoid Mary but only with E. coli. Will we eventually find out that humans can carry and shed the bacteria just like cattle do without becoming ill? Sounds like a good thesis for a microbiology grad student to me.

Guy H Loneragan, Texas Tech University

It appears that E. coli O104:H4 with a MLST Sequence Type=ST678 was observed approximately 10 years previously in Germany in a HUS case.

Like the current outbreak strain, it was stx2 positive and eae negative. I am unsure of the status with the EaggEC Virulence plasmid in the 2001 isolate.

Rather than hypothecate an ill worker contaminating wash water (which would likely only lead to a few sporadic cases), consider the possibility of use of unpasteurized human waste as a fertilizer. This would more likely lead to a large scale outbreak.